Dish reflector with adjustable subreflector



April 8, 1969 A. A. BRACCINI 3,438,045

msn REFLECTOR WITH ADJUSTABLE SUBREFLECTOR fined Feb. 23, 1966 Sheet INVENTOR. Amt/6&4 mad/A4 BY Z700 fi k April 8, 1969 A. A. BRACCINI 3, 3 ,0

DI SH REFLECTOR WITH ADJUSTABLE SUBREFLECTQR Filed Feb. 23, 1966 Sheet INVENTOR.

#l/Ma 4 WCCW/ April 8, 1969 A. A. BRACCINI 3,438,045

DISH REFLECTOR WITH ADJUSTABLE SUBREFLECTOR Filed Feb. 23, 1966 I Sheet 3 INVENfi; ,dl/ a/l a A 3&(0/V/ 85 BY 944/ M a Arm/4s United States Patent Ofitice 3,438,045 Patented Apr. 8, 1969 US. Cl. 343-883 Claims ABSTRACT OF THE DISCLOSURE A large parabolic antenna has a subreflector centrally mounted. The subreflector is adjustably positioned using elongated adjustment slots extending in mutually perpendicular directions corresponding respectively to a horizontal and vertical adjustment of the subreflector relative to the parabolic antenna. A third adjustment involving a lead screw allows the subreflector to be adjustably positioned either closer to or farther from the parabolic antenna along its axis. The parabolic antenna is constructed using a central ring with two spaced flanges thereon forming an annular pocket into which one end of each of a first series of spaced and radially extending rib structures is snugly fitted and releasably secured. The other end of each of such rib structures is constructed such that their outer ends are interconnected by a series of intercostal plates which extend generally along a circle and also for releasably securing thereto a second series of spaced and radially extending rib structures with each being aligned with and serving in general as a prolongation of a corresponding one of the first series of rib structures. A series of intercostal members interconnect adjacent ones of the second series of rib structures which are also interconnected by a torsion member.

The present invention relates to improvements in antenna constructions particularly of those types using a parabolic antenna having a diameter, for example, of l826 feet.

It is desirable in the production of antennas to have the capability of manufacturing the parabolic reflecting structures in various sizes to fulfill the Wide needs of satellite communications, precision tracking, radio astronomy and millimeter wave research. The present invention is addressed to this particular problem and has as its general purpose, to provide a means of utilizing a common parabolic curvature (100.8" focus) for various apertured (18-26 diameter) reflectors.

The present arrangement for these particular purposes allows the use of common tooling and component parts in the fabrication of the various reflectors; permits maximum transportability and rapid erection; provides high surface accuracy and high rigidity as required by X- and K-band operation; and further, provides ready adaptation for mounting, i.e., versatility in the pedestal to reflector interface.

Using the teachings incorporated herein, the antenna is not limited either with respect to aperture size or pedestal installation and results in inexpensive construction considering the fact that engineering and tooling may be amortized over a plurality of units.

It is therefore an obect of the present invention to provide improved means and techniques whereby the a-bovedndicated new results, advantages and desirable features may be obtained.

Another object of the present invention is to provide reflectors of this character which may be used with either focal point or Cassegrainian type feeds.

Another specific object of the present invention is to provide a construction of this character wherein an unobstructed area is provided to the rear of the reflectors vertex for installation of microwave equipment.

A specific object of the present invention is to provide a construction of this character obtaining the above-indicated results and desirable features using a reflector having a paraboloid reflective surface contour having a focus of 100.8 inches and providing focal distance to diameter (F/D) ratios ranging from 0.32 for 26 foot diameter reflectors to 0.47 for the smaller 18 foot diameter reflectors.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. This invention itself, both as to its or ganization and manner of operation, together 'with further objects and advantages thereof, may be best understood by reference to the following description taken in connection with the accompanying drawings in which:

FIGURE 1 is generally a transverse sectional view through the reflector structure of an antenna embodying features of the present invention, the view illustrated being taken substantially as indicated by the arrows of the lines 1 1 in FIGURE 5;

FIGURE 2 is a sectional view taken substantially as indicated by the line 2-2 in FIGURE 1;

FIGURE 3 illustrates in enlarged form some of the structure illustrated in FIGURE 1;

FIGURE 4 is a view taken as indicated by the lines 44 in FIGURE 3;

FIGURE 5 is a view taken as indicated by the lines 55 and illustrates the back of the antenna reflector const-ruction;

FIGURE 6 illustrates a portion of FIGURE 5 but in enlarged form;

FIGURE 7 is a vie-w taken as indicated by the lines 77 in FIGURE 6;

FIGURE 8 is generally a transverse sectional view through the subreflector assembly and corresponds generally to a sectional view taken along the lines 88 in FIGURE 9; and

FIGURES 9 and 10 are views taken as indicated by the corresponding lines 9-9 and 1010 in FIGURE 8.

In general, the antenna as shown in the drawings, incorporates a main parabolic reflector 10 made up of 16 panels 10A and a subreflector 11 supported by four spars 12, one end of each of the spars 12 being secured to the backup supporting structure 14 for the reflector 10 and the other ends of each of the spars 12 being secured to a frame 15 on which the subreflector 11 is adjustably mounted for adjustment in three dilferent directions whereby the subreflector 11 may be properly oriented with respect to the main reflector 10.

Each of the sixteen panels 16A are of conventional aluminum honeycomb sandwich type construction in which suitable fastening means are provided for securing the individual panels to the backup structure 14. Such means incorporated in the panels may, for example, be of the character described in the copending application of Jerry Laibson and Robert M. Munro, Ser. No. 424,102, filed Jan. 7, 1965, now US. Patent 3,383,692, issued May 14, 1968, and assigned to the same assignee as the present application.

Actually, the backup structure referred to by the general reference numeral 14 is composed of dilferent components or subassemblies, namely, a center hub assembly 17, sixteen radial ribs 18, sixteen intercostal members 19 (FIGURE 5), and eight torsion braces 24.

The center hub assembly 17 is common to all diameter reflectors in the production series. The ribs 18, however, are of ditferent lengths depending upon the particular diameter of the reflector. These ribs 18 are each formed by a casting process and the dilferent required sizes of the same may be made in essentially the same mold to which various sections may be added for an increased length of the rib 18. In all cases, that portion of the rib 18 or casting which abuts the center hub assembly 17 is always the same but a diflerent portion of the mold may be added or subtracted for the purpose of making a longer or a shorter rib 18 as required.

The center hub assembly 17 is composed of elements which may be enumerated as follows:

(1) A centrally located flanged ring 20 (FIGURE 3), the ring 29 having two flanges 20A and 293 that define a deep annular peripheral grooved portion 20C within which,

(2) A series of sixteen inner rib structures 21 are fitted and bolted using a series of bolts 22 (FIGURE 4), and

(3) A series of intercostal plates 23 (FIGURES 3 and 7) which extend between and are secured, for example, by bolts or welding to outer adjacent ends of inner rib structures 21.

For these purposes it will be seen in FIGURES 3 and 4 that'the inner ends of each of the rib structures 21 is formed with a protruding rectangular portion 21A which is snugly received within the ring grooved portion 20C and bolted thereto by a series of bolts 22.

Each of the rib structures 21 in the form of a casting is cast in the form illustrated in FIGURE 3 wherein the outer boundaries are defined generally by four sides with one of such sides 2113 having end portions 210 and 21D adapted, as for example, by providing corre- Sponding apertured portions 21E, 21F for securing of the composite reflector to a suitable supporting structure (not shown). The particular shape of the rib 21 may be modified to provide, for example, instead of a four-sided configuration as shown in FIGURE 3, only a three-sided configuration wherein, in this latter case, only the end t portion 21C is available with its apertured portion 21E for securing to a mounting structure.

Each of the sixteen outer rib structures 18 is secured to a corresponding inner rib structure 21 by two bolts 25, 25 as illustrated in FIGURE 3.

Each of the inner ribs 21 and each of the outer ribs 18 is formed with ear portions to which the panels 10A are secured. It will be seen as in FIGURE 5 that adjacent abutting edges of panels 19A extend in the same radial direction as the joined ribs 21, 18 and that Whereas the inner rib 21 has only one pair of panel securing ears 21H, each of the outer ribs 18 is formed with two pairs of panel securing ears 18H and 18].

The means for securing the panels 10A to the ear portions of the ribs 21 and 18 are shown in the form of bolts that extend through the rib ear portions and are threaded in inserts within the panels 10A in, for example, the manner described and indicated above with reference to the above-mentioned copending patent application.

The inner ends of the joined panels 10A define an open circular portion which in the present instance is illustrated as being closed by a metal disc 32 which has a series of L-shaped bracket elements 32A secured thereto, the inner ends of the elements 32A being secured to the ring 243 by fastening elements 323 (FIGURE 3).

The intercostal elements 19 are each illustrated in the form of a tubular element 35 to which a plate 36 is secured as, for example, by first providing a slit in the end of the tube 35, inserting the plate 36 in such slit and then welding the plate 36 to the tube 35. By using such techniques a flat surface is provided which is more suitable for fastening to the ribs 18 as, for example, by bolting or by welding.

The braces 24 may also be of tubular stock having their ends adapted for securing to adjacent ribs 18.

In those instances, where the antenna is of larger diameter, the ribs 18 are prolonged and additional ears like ears 183 and 18H are provided on the added length of the ribs 18 and also additional intercostal members,

4 like the intercostal members 15, extend between and interconnect such added portions of the ribs 18 with, of course, the ears in such added portions also serving as additional fastening means for the larger diameter panel sections 10A.

The previously-mentioned subreflector supporting spars 12 may be secured to rib structures 18 in the manner illustrated in FIGURE 2 wherein spar 12 has a threaded portion 12A adjustably secured to the rib 18 usinthe three nuts 12B, 12C and 12D.

The subreflector I1 is mounted for independent adjustment in three mutually perpendicular directions using the structure now described in relation to FIGURES 8-l0.

The subreflector 11 has four bolts 40, 41, 42 and 43 extending through vertical slotted portions 45A, 45B, 45C and 45D respectively on a ring 45, the ring 45 being secured concentrically on a tubular member 47 by weld 48. It will be observed that the reflector 11 is adjustably held on such ring 45 by the four nuts 50 threaded on the bolts 4043 and further, it will be seen that the reflector 11 may be adjusted in a vertical direction by loosening such nuts, moving the reflector 11 up or down as desired to the desired position and then the nuts are tightened to secure the vertical adjustment.

The tubular element 47 is formed with a guide slot 47A within which a pin 52 extends, such pin 52 being secured to the outer tubular structure 53 whereby the inner tubular structure 47 may be moved linearly, either closer or further from the main reflector 10 without rotation of the tubular structure 47 in the outer tubular structure 53. For effecting such movement the inner tubular structure 47 is closed by a disc 55, such disc 55 being centrally apertured to receive a bearing structure 57 on a lead screw 58. The bearing 57 is retained by nut 60. The lead screw 58 is threaded in a centrally apertured portion of disc 60 welded within tube 53 so that when the lead screw 58 is turned by turning the knurled knob 62 on screw 58, the inner telescoped tube 47, with the reflector 11 mounted thereon, is moved closer to or further from the main reflector and without rotation of such reflector 11 about its axis. After the knurled nut 62 is thus adjusted, such adjustment may be secured by clamping the outer tube 53 around the inner tube 47. For this latter purpose the tube 53 is split at 53A (FIGURE 10) and is formed with two end plates 53C and 53D through which a clamping bolt 53F extends. Such bolt 53F meets the nut 536 which When tightened, clamps the outer tube 53 to the inner tube 47 to thereby secure the adjustment previously effected by knob 62. The outer tubular housing 53, in turn, is adjustably mounted for adjustment in the horizontal direction. For that purpose a ring is welded on tube 53 and such ring 70 is braced by a series of braces 71, also welded to the tube 53. This ring 70, as seen in FIGURE 9, is provided with four horizontally extending slotted portions 72, 73, 74- and 75 through which corresponding bolts 78, 79, and 81 extend for adjustably securing such ring '70 to a mounting plate 84- to which is welded or riveted a series of circumferentially extending plates 85, such plates 85 defining an octagonally shaped structure. Such plates 85 are suitably braced using a series of braces 87 extending between the face plate 84- and the peripherally extending series of plates 85. 1

An end of each of the four spars 12 is secured to alternate ones of these octagonally arranged plates 85. As shown, the spar ends 12 have a plate 12E Welded thereto and such plate 12E is bolted to the face of a correspondin plate 85.

Thus it will be seen that the reflector 11 may be adjusted in any one of three directions with each of the adjustments being independent of each other.

While the particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

I claim:

1. In an antenna construction of the character described, a ring structure having a peripheral base portion from which a pair of spaced annular flange portions extend outwardly to define a deep annular grooved portion at the periphery of said ring structure; a plurality of inner rib structures each having an inner end portion snugly received by said grooved portion and releasably secured to said base portion and extending radially outwardly of said ring structure; a plurality of outer rib structures extending radially outwardly with each being releasably connected to a corresponding inner rib structure; reflector panels connected to said inner and outer rib structures.

2. A construction as set forth in claim 1 including circumferentially extending intercostal support members extending between adjacent outer rib structures and being connected thereto at points of equal distance from the center of said ring structure; and brace members extending between adjacent outer rib structures and being connected thereto at points of unequal distance from the center of said ring structure.

3. A construction as set forth in claim 1 including intercostal plates interconnecting the outer ends of adjacent inner rib structures.

4. In an antenna construction of the character described, a pair of telescoping elements, means acting between said elements for preventing rotation yet allowing sliding movement of one relative to the other; means for moving said one element relative to said other element; a first flange on said one element; a second flange on said other element; a reflector; a supporting structure; means mounting said reflector on said first flange; means mounting said second flange on said supporting structure, said first flange having an adjustment slot through which releasable fastening means extend for fastening said reflector to said first flange, said second flange having an adjustment slot through which releasable fastening means extend for fastening said second flange to said supporting structure, the adjustment slot in said first flange and the adjustment slot in said second flange extending in mutually perpendicular directions.

5. A construction as set forth in claim 4 in which the outer one of said telescoping element is partially split longitudinally to provide two end portions; and means on said outer element for moving said end portions together to clamp said inner element to said outer element.

References Cited UNITED STATES PATENTS 2,003,171 5/1935 Burrell 343-781 3,153,789 10/1964 Ashton 343-912 3,234,550 2/1966 Thomas 343912 3,235,872 2/1966 Schepis 343-912 OTHER REFERENCES RCA in No. 613, March 1965.

ELI LIEBERMAN, Primary Examiner.

US. Cl. X.R. 343-781, 912 

